Interchain-Expanded Vanadium Tetrasulfide with Fast Kinetics for Rechargeable Magnesium Batteries

Magnesium batteries are promising energy storage systems because of the advantages of low raw material cost, high theoretical capacity, and high operational safety properties. However, the divalent Mg2+ has a sluggish kinetic in the cathode materials which resulted in poor electrochemical performance. Many strategies were adopted to improve the mobility of Mg2+ in the host structures. In this paper, we report on the optimization of chain-like structure VS4@reduced graphene oxide (VS4@rGO) through expanding interchain distance to increase the ion diffusivity. By combining theoretical calculations and experimental investigations, the expansion of interchain distance and reversible intercalation of MgCl+ are revealed. With the fast kinetics of MgCl+ (instead of Mg2+) intercalation into expanded VS4@rGO, higher capacity of 268.3 mA h g–1 at 50 mA g–1 and better rate capability of 85.9 mA h g–1 at 2000 mA g–1 have been obtained. In addition, the expanded VS4@rGO framework shows a high specific capacity of 147.2 mA h g–1 after 100 cycles and a very wide operating temperature range (−35 to 55 °C). The high discharge capacity, excellent rate capability, and broad temperature adaptability demonstrate promising application of VS4@rGO in magnesium batteries.